The present invention relates to plastic containers for beverages.
Food containers, including beverage bottles, can be molded from a plastic, such as polyethylene terephthalate (PET). Permeability of such bottles may be undesirable, since ingress of oxygen and egress of carbon dioxide can degrade food quality. Permeability can be reduced by blending the plastic with permeability-inhibiting additive before molding the plastic into the food container. For example, clay is sometimes used as such an additive.
The present invention comprises a method of forming an intermediate composition. The intermediate composition is to be added to a polymer, or to a polymer precursor, in a process of manufacturing a low permeability container formed of the polymer or polymer precursor. One manner of performing the method comprises forming an intermediate composition which, if added to the polymer or polymer precursor, will inhibit the permeability of the low permeability container subsequently formed of the polymer or polymer precursor. The forming step comprises mixing a solid dispersant with clay to form the intermediate composition as a solid.
In a preferred embodiment, the intermediate composition is free of the polymer or polymer precursor and is also free of water. It is advantageous for the clay to be exfoliated within the dispersant in the forming step. The clay is preferably a smectite, and is most preferably montmorillonite. The dispersant is preferably a wax, and is most preferably castor wax. The polymer is preferably a thermoplastic, and is most preferably a polyester, such as PET.
In another manner of performing the method, a permeability-inhibiting additive is mixed with a dispersant that is solid at room temperature to form a mixture which comprises the additive and the dispersant. The method further comprises dispersing the additive within the dispersant while maintaining the mixture at a temperature above the melting point of the dispersant. The method still further comprises cooling the mixture to a temperature below the melting point of the dispersant to form an intermediate composition which is solid and which, if added to the polymer or polymer precursor, will inhibit the permeability of the low permeability container subsequently formed of the polymer or polymer precursor.